Adapting Keep on the Shadowfell to Mystara

Here's a Mystaran adaptation. I'm assuming some familiarity with Karameikos:

Change Winterhaven's name to Luln (This will require making it a bigger place, though). Replace Lord Paidrag with Mistress Sascha (Human Fighter 8). She is mainly focused on the menace of the Black Eagle Barony and eager to employ adventurers to deal with what she sees as minor threats which would leave Luln too vulnerable if she had to deploy the militia and her handful of professionals to deal with them. The temple of Avandra becomes a temple of the Traladaran faith (The Church of Karameikos should have a single representative in town, Father Antonius, who has to lead a tiny congregation out of his house. With no Thyatian-descent lord in Luln, few of the locals have any interest in abandoning their old faith.)

The Keep on the Shadowfell becomes Koriszegy Keep. Two hundred years ago, Baron Mikhail Koriszegy was eager to unite Western Karameikos, maybe even the entire land of the Traldars under his control. However, his attempt to conquer Halag as a start ended only in defeat. Frustrated, he turned to the worship of the Entropics in search of power. In his foolish desire for power, he listened to a Cleric of Loki (Grigori Andreson), only to be tricked into opening a portal to the Shadowfell. The ritual went awry, as Baron Mikhail proved insufficient to performing the ritual correctly. He and Grigori were both reduced to the state of slime monsters (the Blue Slime and the Ochre Jelly in the adventure.) This left the portal partly open for monsters to rampage out of, devastating the countryside. Fortunately for Karameikos, a gold dragon named Shimmerclaws had been observing Baron Koriszegy, and was able to force the portal shut, but at the cost of his own life. His servants buried him nearby, and erected wards to confine the once human slime-monsters in a set of caverns close to the site of the ritual itself, beneath the keep.

For 160 years, the castle lay empty, with none willing to try and live in it. The Kalinkov noble clan took over control of the area, ruling from the town of Luln. Andrei Kalinkov became Baron of Luln in 953 AC; he wanted to reclaim Koriszegy Keep and make it the capital of what he hoped would be a greater Traldar state. Aided by a cult which believed him to be Halav reborn, he moved into the Keep, purified it as best he could, and set it up as his new capital, leaving Luln to be overseen by one of his knights, Sir Alexis Korrodov. He sealed off the entire cave complex with a new wall, purified the various dungeons, and prepared what would have been the tomb of Baron Mikhail Koriszegy to serve as a family crypt when his own death came, turning the antechamber to it into a temple to Halav.

His show of power, apparently defeating the curse of the Keep, helped to attract warriors to his cause, and at the height of his power in 960 AC, he even conquered Halag, wiping out its ruling clan (the Halag family) and replacing it with one of his younger sons, Anton Kalinkov. However, these wars were expensive, and the town of Luln had grown resentful of being used as a milk cow to pay for Andrei's wars.

Worse, the rift still existed, though mostly sealed, waxing and waning according to shifts in the balance of the planes. Slowly, its influence began to eat away at the sanity of the Keep's inhabitants, finally leading to Count Andrei Kalinkov of the Western Lands (as he now titled himself) snapping and launching a slaughter of his own men, aided by rampaging undead, the souls of those who had died the night of Baron Mikhail Koriszegy's great mistake. In his delusion, he was trying to overcome Baron Mikhail's men in order to stop the rift from being opened. Instead, he slaughtered his own family. Those of his retainers who survived sealed him into the crypt he'd already prepared and tried to sanctify the chapel of Halav enough so he couldn't escape.

The Burghers of Luln refused to let Baron Anton Kalinkov of Halag, the only surviving member of the family take the throne of Luln, declaring they would govern themselves. Anton wasted the strength of Halag in a series of failed attempts to conquer Luln.

Finally, in 970 AD, Baron Ludwig von Hendriks easily conquered Halag and renamed it Fort Doom, executing Anton and marrying his daughter Anastasia in order to lay claim to Luln. Luln, however, told him to forget about it, and he's been trying unsuccessfully to claim the place ever since.

Kalarel (born Julius Negrus, changed his name when he became a priest of Orcus) is the ambitious Hattian son of one of Baron Ludwig's major followers, Sir Cornelius Negrus. He is jealous of Bargle and wishes to pull off a grand coup to gain the same prestige / baronial favour which Bargle possesses. Having heard of the tragedies of Koriszegy Keep, he believes there to be a rift to the Shadowfell there. He hopes to re-open it and raise an army of undead and Shadowfell creatures to bring to the service of the Black Eagle Baron, thus balancing the influence Bargle gains through his alliances with the humanoids of Western Karameikos.

Irontooth, however, is one of Bargle's allies, one of the many humanoid lords he has helped come to power over humanoid tribes in order to bring them under his sway. His suit of magical armour is a gift from Bargle (Perception DC 20 will find the Maker's mark, one of the blacksmiths of Fort Doom (Otto), worked into it. Arcana DC 25 or History 20 to connect that mark to Fort Doom). Irontooth is working under the assumption that Kalarel works for Bargle and Baron Ludwig. He thinks Kalarel is preparing the Keep for him to move into, as part a prelude to taking over the whole area, which he will rule for the Black Eagle Baron (Ahh, the joys of inflated Egos.) Should evidence to the contrary be presented, a skill challenge can be attempted to persuade him to aid in eliminating Kalarel. (This requires 4 successes before 3 failures with the skills Bluff at DC 15, Intimidate at 25, Diplomacy, History, Arcana (Both of which can be used to convince Irontooth the place is a death-trap) at 20, other skills probably at 25, but possibly lower if you think of something sufficiently appropriate).

Ninaran is a member of the Callarii elf clan, but has become an Orcus cultist and now serves as Kalarel's spy in the town and his go-between with Irontooth and the Kobolds. She is somewhat loyal, but will choose spilling the beans on Kalarel over being killed if forced to the choice. Her personal testimony to Irontooth that he's been tricked reduces the difficulty of the skill challenge to persuade him to help deal with Kalarel by 5.

Bairwin Wilderson (area 7 of the town map, Human Mage 4 (see MM 163)) is actually the local spy for the Iron Ring, to whom he will report the existence of the adventurers. He will avoid any confrontation with the PCs and happily sell them goods. If he learns of them (and short of them remaining extremely covert, he will), he sends a message to his bosses which will eventually lead to the Iron Ring and its Hobgoblin allies, the Bloodreavers, trying to ambush the PCs on one of their trips around the area:

Encounter I-1: The Iron Ring StrikesLevel 3 (762 XP)

1 Human Guard, Level 3 Soldier

1 Human Bandit, Level 2 Skirmisher

6 Human Rabble, Level 2 Minions

1 Hobgoblin Archer, Level 3 Artillery

4 Hobgoblin Grunts, Level 3 Minions

The two forces will pretend to be fighting each other until the PCs approach, then attempt to knock all the PCs out, loot them, and drag them off to be taken to Fort Doom, then shipped for sale in Thyatis. Should the PCs lose, the DM will need to improvise for that contingency.

Loot: A note which implicates 'Agent Q' in Luln as behind the attack (Interrogating either of the non-minion humans can give a good enough description to figure out Bairwin is Agent Q), 13 5 GP silver rings with the Iron Ring's sigil on them, 12 GP, 390 SP.

Bairwin knows Kalarel has been buying slaves, but isn't sure why, though he assumes they're probably intended to be human sacrifices.

Run On the Road: Kobold Brigands as written, but make sure the Kobolds talk about how their Lord Irontooth will soon rule this area, how Lord Bargle favours them, their servant Kalarel, etc, etc. Enough to make it worth the PCs time to take one alive to find out what the Kobolds think is going on.

A group of cranky teenage halflings from the Shires who have formed a Striker band are trying to get revenge for the death of several of their friends at the hand of the Black Eagle's Men. Somewhat lost, they now think they are in the Black Eagle Barony and are preparing to ambush and kill anyone who looks like a Black Eagle minion to them...which is to say any group of armed people that have anything taller than a halfling in it. They're not entirely crazy, so if the players listen to them rant in battle, they can try a 4/3 skill challenge (DC 20 for diplomatic skills, Perception, or History) to convince the Hin they aren't servants of the Black Eagle Baron. Should the PCs succeed at that, the Hin will be so mortified by their mistake they will give half their treasure to the PCs as an apology and warn them of where the Kobold lair is and how dangerous it is. They can also tell the PCs about the archaeological dig, but they don't realise it's been taken over.

2 Halfling Thieves, Level 2 Skirmisher

2 Halfling Slingers, Level 1 Artillery

6 Halfling Stouts, Level 2 minions

Treasure: 10 3 GP ornately carved Copper Bracelets with an open hand symbol (the sign of this group, 'The Band of the Hand'), 10 GP, 470 SP. If they are paying an apology, they give the PCs 5 GP and 385 SP)

A-2 and A-3 need little modification except to place Nithian style art inside the caves; the kobolds are living in an old tomb complex built by the Nithian Traldars when they first came to Karameikos millennia ago. It has long ago been looted. (Or, if you wish to add an extra encounter or two, there can be a concealed inner tomb entrance to a tomb of the DM's own design). The message from Kalarel should be rewritten to mention Bargle and the Black Eagle and Kalarel's claims he is 'preparing' the castle.

A-4 is the site where Shimmerclaw was buried. By digging up his body and desecrating his burial, the archaeologists have unwittingly weakened the wards he created on the keep--the caves of the slimes are no longer sealed or blocked off, and Kalarel can now more easily open the rift. (Appropriate Arcana and History checks may pass some of this info to the PCs.) However, Kalarel wants the mirror which was one of the foci of the ritual to assist in his work in opening it yet more easily.

The gnome and the Halfling know of Kalarel's manipulation of the Kobolds and can be used as a source of evidence to try and persuade Irontooth to turn on Kalarel.

Rather than being sceptical of Orcus cultists per se, the locals of Luln will assume any such evidence is connected to the Black Eagle Baron in some manner, since they see his minions behind every rock, some days. The note from Irontooth's lair will motivate Mistress Saschia to offer a reward for dealing with Kalarel.

Optionally, some locals may blame the Church of Karameikos, asserting it must be a front for Orcus worship; the PCs may have to try to save the unfortunate Father Antonius from an angry mob. (Mistress Saschia herself will not approve of any such lynching.)

Father Antonius, if saved from the mob or simply approached by the PCs with evidence of Orcus cultists, will gift the PCs with 4 bottles of holy water he has blessed:

Holy Water Bottle This can be thrown as a light thrown weapon, Range 5/10. On impact, it explodes in a Burst 1. Roll to hit for all targets. It does damage to Undead only: 2d6+3 radiant damage to any undead in the central square, 1d6+3 radiant damage to any in the adjacent squares.

(If thrown at the Thing in the Portal in the final encounter, the Thing is stunned until the end of the thrower's next turn on a successful hit.)

Shadowfell Keep Level One

Most of the encounters on this level can be run as written with a few exceptions:

Area 3: The Holy Symbol is one of Halav

Area 5: The undead wear the livery of House Kalinkov

Area 6: The undead wear the livery of House Koriszegy and the armour to be found within the armoury belonged to Baron Mikhail Koriszegy. If the Ochre Jelly (which was once him) sees it, it will retreat out of a sense of shame if possible. Any undead in Koriszegy livery will not attack its wearer unless he hits them first.

Area 7: The undead wear the livery of House Kalinkov. The shrine is sacred to Halav.

Area 7: Rename Sir Keegan as Count Andrei Kalinkov of the Western Lands. He has pretty much the same motivation set as Sir Keegan, but knows the earlier historical material and can tell the PCs all about it.

Area 9: The Ochre Jelly here is all that's left of Baron Mikhail Koriszegy, now an immortal slime monster. He fights more intelligently than a normal Ochre Jelly and the rats obey him. His goal, however, is to die. He wants an end to his suffering, but due to Grigori's continuing influence over him, he can't just sit there and wait to be killed. Confronted by someone in his old armour, however, he flees in shame back to his 'lair'. PCs who know who he is, can try a difficult (8/6) skill challenge to break Grigori's hold on him (using Religion, Arcane, Diplomacy, Dungeoneering, and History). He will help them kill the Blue Slime, then beg for death as best a slime that can't talk can beg for death.

Area 10: Change this into a ritual space used by Grigori/the Blue Slime in preparation for his plans to let Kalarel open the rift, then capture him and switch bodies with him to escape his doom as slime boy. It is guarded by several petty creatures which Grigori has managed to summon:

Miskos flees if he seems likely to die. He gleefully betrays Grigori if captured. Not that he knows much useful...

Area 11: The Blue Slime is Grigori; it fights intelligently, and runs if it has to, if it can. Grigori hopes to eventually steal Kalarel's body with one of his rites, if Kalarel succeeds. The old hobgoblin note should be removed from this room.

Interlude 3: This can be run as written, keeping in mind Ninaran's place in the setting and her knowledge. If captured, she will threaten that Kalarel's father will avenge her or Kalarel, and so will the Black Eagle, if she is killed (or Kalarel is)

Level 2 of the Keep: Most of this can be run as written with some notes below:

Area 14: The vicious Short Sword has Otto's maker mark, just like the magic chainmail Irontooth had. Warchief Shalak knows Kalarel's ancestry, and like Ninaran, will threaten the PCs with revenge if they gain the upper hand over him.

However, if the PCs can succeed in a 6/4 skill challenge, they may be able to trick him into thinking the PCs work for Bargle, who has sent them to defeat Kalarel's ploy; he fears Bargle taking revenge on him for betraying Bargle and serving Kalarel. This can get him to surrender to them and help to overthrow Kalarel. But it may be hard for the PCs to figure this out unless they recognise the blade's origins and know other back-story material.

Area 15: If they know of Grigori and Mikhail, the PCs may think the G. Cube used to be someone important, but it's just a monster. The Corruption Corpses, however, as Count Andrei's two elder sons and will flee from the sight of his blade if the PCs have it.

Area 16: This is a statue of Halav. Replace the Cherub statues with statues of Petra, Zirchev, Chardastes, and Tarastia.

Area 17: The undead here wear Koriszegy livery and the ghoul was once Maria Koriszegy, wife of Mikhail, though the PCs are unlikely to chat with her and find out.

Area 18: The Underpriest is Hybaros (once Sir Marcus Kommenus, cousin of Kalarel). The two berserkers are former Storm Soldiers turned Orcus cultists. They still dress like Storm Soldiers. The vampire spawn are former Karameikan peasants, enslaved by the Iron Ring and turned into slaves, then sacrifices and now Vampire spawn.

Area 19: Kalarel will try to bribe / recruit the PCs before trying to kill them, as he fears a long fight will lead to a disaster like that which happened to the Koriszegy clan. He offers them a place as his henchmen when he gains the favour of the Black Eagle Baron and basically plot-exposits anything the DM needs him to. (He is, in fact, sincere-ish, which is to say, that if for some reason they take him up on it, he will employ them as significant flunkies, though always watching for betrayal. He knows he needs strong supporters if he is to ever overthrow Bargle and take his place.) PCs who bluff working for Bargle will make him go utterly berserk in an effort to defeat them.

PCs who fake accepting his offer can try to sabotage his rite once he resumes it; should they succeed, the Thing in the Portal will eat him and the PCs will have to try and find a way to seal the rift (design an appropriate skill challenge)

Among the loot, the PCs will find records indicating Kalarel's dealings with the Bloodreavers/Iron Ring and indicating they have a base in Thunderspire Labyrinth.

PCs may also be able to take dead vampire spawn back to their families for burial too.